This invention relates to a threaded fastener and washer assembly and more particularly to a preassembled threaded fastener and washer assembly for use in connection with aluminum panel roof construction.
There have been many attempts to provide a threaded fastener and washer assembly suitable for securing relatively thin metal panels or workpieces together. Securely fastening two such thin metal workpieces together has been difficult due to the tendency of the threaded fastener to strip the associated panels under relatively high torque. The sealing characteristics of such fasteners were also deficient due to the inability to manufacture a screw which has a thread immediately beneath the clamping surface of the head of the screw.
Many attempts have been made to provide a sheet metal fastener assembly that effectively forms tight waterproof joints. For example the invention of prior art U.S. Pat. No. 3,661,046 utilized a combination of a threaded fastener with an upper threaded portion and a compressible sealing washer which provided an effective seal in sheet metal environments. However, the joint between sheet metal panels for metal roof or building construction must be extremely tight to withstand environmental factors. While the above noted prior art threaded fastener has met with a certain amount of success, total effectiveness and efficiency of such fasteners can still be greatly improved.
Accordingly, it is an object of the present invention to provide an improved preassembled threaded fastener unit for use in metal roof or building construction which will effectively and tightly join sections of relatively thin sheet metal panels without stripping the panels.
It is a further object of this invention to provide a preassembled threaded fastener unit which will effectively join sheet metal panels and provide a protective weatherproof seal.